Press control electrical and pneumatic interlocking



United States Patent [72] Inventor Edward J. Freeland 2,959,263 11/1960Simson 192/131UX Hastings, Michigan 3,004,647 /1961 Andrus et a1. 192/142 [21] AppL No. 768,403 3,019,878 2/1962 Munschauen. 192/131UX [22]Filed Oct. 17,1968 3,249,820 5/1966 Stimmel ..l92/129(.2)UX patmed 20,1970 Primary Examiner-Mark M. Newman Asslgnee Guns Western lnd'mnalPmducs Assistant Examiner-Allan D, l-lerrmann p y Attorney-Meyer.Tilbery and Body Grand Rapids, Michigan a corporation of Delaware, bymesne assignments ABSTRACT: A press control system which includes aclutch mechanism and a pneumatic circuit for actuating the clutchmechanism, including a clutch valve. An electrical run circuit m l Iactuates the clutch valve, the circuit comprising dual run-jog [54]ELEMCALAND PNE TIC buttons which must both be depressed for energizingthe cir- 7 Cl 3 Dr cuit. The circuit also includes a holding switchwhich permits alms awmg the flow of current to the clutch valve solenoidwhen the dual [52] US. Cl 192/129. run-jog buttons are released, and anantirepeat relay which 192/ 18, 192/142 revents repeat strokes in theevent the run-jog buttons [51] lnt.Cl Fl6d 9/00, remain in the depressedposition. The improvement of the Fl6d 67/04, F16d 7l/00 presentinvention comprises an interlock arrangement Field of Search l92/l2(.2),between the pneumatic circuit and electrical run circuit in- 2 1, 142, 1cluding switch means actuated by said clutch valve to prevent the flowof current to said antirepeat relay means in the event References cuedof a malfunction on the part of components of the electrical or UNITEDSTATES PATENTS pneumatic circuit, or through said holding switch untilthe 2,818,150 12/1957 Eck et al 192/144 clutch valve Opens 34 L" 7 1 w c.4 w T T I -z Jig 'f f,

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Sheet 1 of 2 FIG.I E LSA LSB h AASTER SOL f RPQW Q H AIR VALVE 51, ISUPPLY LI] fa- Hl- 24 D pnsss DCI 2 ma SWITCH 20/22 F naw c TCH CAMS 26LU g MOTOR RLS-l RLSZ RLsa RLS4 ROTARY LIMIT SWITCH SETTING FIG.2A

INVENTOR.

EDWARD J. FREELANE BY 77 f5 AT ORNEYS.

PRESS CONTROL ELECTRICAL AND PNEUMATIC INTERLOCKING The presentinvention pertains to the art of controls for machines, and moreparticularly to a novel control arrangement for presses of thereciprocating type.

The invention is particularly applicable to controls which utilize bothan electrical control circuit and a pneumatic actuating circuit, and toa novel safety interlock arrangement between the two circuits by whichone or both of the circuits are deenergized on failure of componentstherein. Although the invention will be described with reference to apress, it will be apparent that principles of the invention areapplicable to other types of machinery.

The invention also is particularly applicable to single-stroke operationof a press or other type of machinery, although the principles of theinvention are applicable to control circuits designed for continuousoperation as well as single-stroke operation.

In a reciprocating press, there usually is provided a motor for drivingthe press, associated with a clutch mechanism which connects the motorto the press crankshaft, and a pneumatic system which actuates theclutch mechanism. Thepneumatic system, in addition to an air supplyutilizes an air'valve which when opened allows the flow of air from theair supply to the clutch mechanism.

A conventional electrical control circuit for the above press uses astart button to energize the motor starter. In parallel with the motorsolenoid is a clutch circuit containing the coil for the air valvesolenoid. An important part of every clutch circuit are twobutton-actuated contacts which are series connected in the circuitrequiring an operator to use both hands to energize the circuit.Frequently the clutch circuit will be divided into a run circuit and ajog circuit which are energized separately, in which case each circuitwould use series connected contacts. Mechanical connections between therun" contacts and the jog" contacts permit the use of a single pair ofbuttons, with the result that these buttons are known as run-jogbuttons.

Although the jog" portion of the clutch circuit usually is set simply bya jog selector switch (allowing the operator to jog or advance the pressin steps by depressing both the run-jog buttons) the run portion of thecircuit, for singlestroke operation, requires the use of a series ofrelays and switches which permit the clutch to be engaged only after anumber of conditions have been met, and cause the clutch to bedisengaged at a particular point in the press stroke.

A frequently used switch in the run" portion of the clutch circuit is aholding switch which connects the clutch coil with the power supplyafter the press has been started. The purpose of the holding switch isto permit the operator to release the run-jog buttons once the press hasstarted, without stopping the press, but the problem is that should thisswitch fail or relays in this portion of the circuit, the clutch coilcould be energized without depressing the run-jog buttons.

Also, there is always the danger that the operator will hold the run-jogbuttons in a depressed position for too long, causing the press toinadvertently repeat. To prevent this, it is conventional practice toprovide in the clutch circuit an entirepeat relay which prevents theclutch coil from being energized, or reenergized without releasing therun-jog buttons and again depressing them.

Although the antirepeat relay provides a measure of safety, it ispossible that even this relay can become stuck in an energized positionin which case its antirepeat value would be lost.

Similarly, other relays or switches could fail, as could the clutchvalve itself, or the coil actuating the valve.

[t is known to provide an interlock between the clutch air valve andrun" portion of the press electrical circuit which utilizes limitswitches actuatedby the air valve poppets interlocked into the circuit.Still, the shortcoming of this method is that if the air valve were tofail in the open position, air would be fed directly to the pressclutch, causing. the clutch to en gage, in turn, causing repeat strokesof the press slide.

It also is known to associate a pneumatic interlock with the clutch airvalve, installed on the valve itself, but this interlock is so sensitivethat it is not often used, and there is no means for monitoring thepneumatic interlock electrically.

Accordingly, it is an object of the present invention to overcome theabove disadvantages, and in particular to provide a novel and improvedinterlocking arrangement which effectively prevents repeat strokes of apress slide or other machine in the event of a failure of components ofeither or both of the electrical and pneumatic circuits for the press.

In accordance with the present invention there is provided apress-control system which includes a clutch mechanism and a pneumaticcircuit for actuating the clutch mechanism, including a clutch valve. Anelectrical run circuit actuates the clutch.

valve, the circuit comprising dual run-jog buttons which must both bedepressed for energizing the circuit. The circuit also includes aholding switch which permits the flow of current to the clutch valvesolenoid when the dual run-jog buttons are released, and an antirepeatrelay which prevents repeat strokes in the event the runjog buttonsremain in the depressed position. The improvement of the presentinvention comprises an interlock arrangement between the pneumaticcircuit'and electrical run circuit including switch means actuated bysaid clutch valve to prevent the flow of current to said antircpeatrelay means in the event of a malfunction on the partof components ofthe electrical or pneumatic circuit, or through saidholding switch untilthe clutch valve opens.

Preferably, the interlock arrangement includes a line in parallel withthe clutch solenoid containing an interlock relay and a normally openswitch which is closed when said clutch valve is in the open position. Anormally open contact in series with the holding switch responsive tothe interlock relay prevents a flow of current through the holdingswitch until the clutch valve has been opened by depressing both therun-jog buttons.

Normally closed contacts in series with the relay for the press motorresponsive to said interlock relay prevents the motor from beingenergized in the event the clutch valve is stuck in the open position.

in a preferred embodiment in accordance with the invention, a mastersolenoid valve is positioned in series with the clutch valve, theelectrical circuit including clutch valve relay means through which theclutch valve and master solenoid valves coils are energized ondepressing the dual run-jog buttons. Switch means are providedresponsive to the position of the master solenoid valve operable toprevent the clutch valve relay means from being energized should themaster solenoid valve be stuck in the open position.

it will become apparent from the above and other embodiments of thepresent invention, that there is provided a novel safety interlockingsystem, including an electrically interlocked series piping of airvalves which insures that all valves, switches and relays must beoperative before the press will run or repeat.

The invention and advantages thereof will become more apparent uponconsideration of the following specification, with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic illustration showing the press pneumatic system inaccordance with the invention;

FIG. 2 is an electrical diagram illustrating an electrical controlcircuit in accordance with the invention; and

FIG. 2A is a graph showing operation of switches of the control circuitof FIG. 2 in accordance with the invention.

Referring to the drawings, the press is provided with a crankshaft A(FIG. 1) which is driven by a motor B through a clutch C, the latterbeing pneumatically actuated by air from an air supply D through amaster solenoid valve E and dual clutch air valve F, the components D, Eand F constituting the pneumatic actuating circuit or portion of thepress. An electrical circuit (FIG. 2) for the press comprises athree-phase supply circuit G which powers the motor B, and a controlcircuit H which is supplied with power from the three-phase circuit bymeans of a transformer l. The control circuit can generally beconsidered as having a first motor start circuit J, and a clutch circuitK, the latter including a run portion L and jog" portion M.

Returning to FIG. 1, the press crankshaft A is actuated by the motor Bthrough the clutch C, engagement of the clutch causing the crankshaft toturn with the motor and raise and lower a press slide. To engage theclutch, both the master solenoid valve E and dual clutch air valve Fmust be in the open position, since these valves are in series with eachother and between the source of air and the clutch.

The dual clutch air valve F is a known valve which comprises identicalseries connected valve mechanisms in a single valve housing. The reasonfor its use in this instance is one of safety since it is essential thatthe press clutch be engaged only after a series of conditions have beenmet. If one of the valve mechanisms fails in the open position, theother valve mechanism is still closed to prevent air from reaching theclutch housing throwing the clutch into engagement.

As will be shown the master solenoid valve E provides a means forinterlocking the press electrical control circuit with the pneumaticcircuit for further safety to prevent inadvertent engagement of theclutch.

Actuation of the dual clutch air valve is by means of solenoids 20 and22 connected to spools for the valves; a third solenoid 24 actuating thespool for the master solenoid valve E for opening and closing thisvalve.

Also illustrated in FIG. 1 is a pressure switch PS-2 connected with theoutlet port for the master solenoid valve E; and four limit switches,RLS-l, RLS-2, RLS-3 and RLS-4, actuated by cam means 26 mounted on thecrankshaft. The functioning of the pressure switch, cam and limitswitches will be described.

Further, as shown in FIG. 1 the poppets for the dual clutch air valve Fare arranged to open and close limit switches LS-A and LS-B, thefunctioning of these switches to be described.

Turning now to FIG. 2, the three-phase circuit G, which supplies currentto the motor B is conventional simply containing normally open contactsM-l, M-2, M-3 which must be closed before current can be supplied to themotor.

To close the contacts, the motor-start circuit J (which includes lines3, 4 and 5 of the control circuit H) contains in line 3 a motor-startrelay M which when energized closes the contacts M-1, M-2 and M-3starting the motor. To supply current to the relay M, a bar-run selectorswitch 28, also in line 3, must be moved to the run position, closingthe contacts 30, and a motor-start button 32 must be depressed closingthe contacts 34 for this button. Also included in the motor-startcircuit are overload contacts 36 opened on overload of the motor, and aplurality of switches and contacts to be described.

Between the motor-start button 32 and the motor-start relay M, a lead 38is connected to the clutch circuit K, which includes lines 7 l5 of thecontrol circuit, the clutch circuit being connected so that the lines 7are in parallel with the motor-start relay M. Included in lead 38 arecontacts 40 closed by the bar-run selector switch 28 when the latter isshifted to the run position.

The run" portion L of the clutch circuit includes lines 7 --11 connectedto the lead 38 through the part of line 7 which contains normally opencontacts M-4 closed when the motorstart relay M (line 3) is energized.Also in this part of line 7 are contacts 44 of a jog-run selector switch46, which are closed when this selector switch is moved to the runposition.

The job portion N of the clutch circuit includes line 12 connected tothe lead 38 through contacts 48 of the jog-run selector switch 46,closed when the selector switch is in the jog position.

At this point, it is also worthwhile noting the existence of the run-jogbuttons 50 and 52, and the contacts 54, 56 (in line 8); 58, 60 (in line9); and 62, 64 (in line 12) of these buttons. The contacts of line 8,items 54 and 56, are normally closed, while those of lines 9 and 12 arenormally open. Such run-jog buttons are conventional, requiring theoperator to use both hands to engage the clutch,-whether the press isbeing jogged or advanced forwardly in steps, or whether the press isbeing run through a desired stroke. Regardless of which operation isbeing performed it is necessary that both of the run-jog buttons bepressed. Also to be noted are coils 66 and 68 (in lines 11 and 12) forthe dual clutch valve solenoids. These coils are connected to therun".portion of the circuit through lines 11 or 9, and to the jog"portion of the circuit through lines 10 and 11.

Line 11 contains a limit switch RLS-l, actuated by cam means 26, and isknownas a holding circuit to transmit current to the coils 66 and 68once the press has started and the run-jog buttons are released openingline 9.

The reason for the use of two clutch valves requiring dual coils hasalready been mentioned, namely if one fails, the other provides abackup. This is also known.

Added to the above circuit in accordance with the present invention, isa line 15 which is connected with lead 38 so that it also is in parallelwith the motor solenoid M. This line contains the coil 70 for thesolenoid 24 of master solenoid valve E of FIG. 1. Also added is a line14, connected in parallel with line 15, containing a relay CRX to bedescribed. Further, to be noted, are switches PS-2, LS-A and LS-B(mentioned with reference to FIG. 1) having switch contacts 72 and 74(for PS- 2) in lines 8 and 11, respectively; and contacts 76, 78, and 82(for LS-A and LS-B) in lines 8, 14 and 14a, respectively. As describedwith reference to FIG. 1, the pressure switch PS- 2 is connected to theoutlet port of the master solenoid valve. The contacts 72 in line 8 arenormally closed, while those in line 11 (item 74) are normally open; buton opening of the master solenoid valve, the positions of these contactschange, so that those in line 8 are opened and those in line 11 areclosed.

It was also described with reference to FIG. 1 that the switches LS-Aand LS-B were actuated in response to movement of the poppets for thedual clutch valve. Accordingly on opening the valve, the normally closedcontacts 76 and 80 in line 8 for these switches are opened and thenormally open contacts 82 and 78 in lines 14 and 14a for these switchesare closed.

With this broad orientation of the electrical circuit, details of thecircuit will now be described, first with respect to run operation ofthe press.

In this respect, this is a single-stroke press requiring the operator torestart the press after each stroke, although the principles of theinvention are applicable to a continuous stroke or multistroke press,which is operable on a singlestroke basis.

With the bar-run contacts in lines 3 and 6 in the closed position,pressing the motor-start button 32 transmits a current to the motorrelay M. If the jog-run button in line 7 is in the run" position, withthe contacts in line 7 closed, the current passes through contacts M4 inline 7; and through the normally closed contacts 54, 56 of the run-jogbuttons, the normally closed contacts 72 of pressure switch PS-2, andthe normally closed contacts 76 and 80 of switches LS-A and LS-B, all inline 8; to energize relay 1CR.

This relay is an antirepeat relay, for single stroke operation of thepress. Although its function will be described in detail, it issufficient to note that it opens normally closed contacts lCR-l and1CR-2 in lines 3 and 4, and closes normally open contacts 1CR-3 in line9, and 1CR-4 in line 7, those of line 7 being hold contacts for therelay. This means that when the contacts of line 8 are opened, afterenergizing the line, relay ICR remains energized through line 7. Also inline 7 is switch RLS-3 actuated by cam means 26 (FIG. 1), relay lCRremaining energized only so long as this switch remains closed.

Line 9, which contains normally open contacts lCR-3 (closed when relaylCR is energized) and contacts 58, 60 of the run-jog buttons, leads totwo clutch relays 2CR and 3CR, lines 9 and 10. These two relays areidentical, and are merely duplicates to reduce the chances of clutchactuation and engagement by virtue of relay malfunction. In thisrespect, the

relays ZCR and 3 CR close normally open contacts ZCR-l, and

-2, and 3CR-l and -2, in lines and 11, for an input current.

to the terminals of the dual clutch valve coils 66 and 68, through lines9, 10 and 11. The relays also close contacts 2CR-3 and 3CR-3 in line foran input current to master solenoid valve coil 70. The importance of therelays should be apparent, since it is only by energizing these relaysthat the clutch is engaged. By having the two relays in parallel, shouldone of the relays fail in the energized position, the clutch would stillnot be engaged because of proper operation of the other relay.

Also energized by relays 2CR and 3CR are normally closed contacts 2ClR'4and 3CR-4 in line 8. Although these contacts will be discussed ingreater detail, they prevent the antirepeat relay ICR from beingenergized should either or both relays 2CR and 3CR fail in the energizedposition.

The primary function of the antirepeat relay can now be discussed.Should the run-jog buttons 50 and 52 inadvertently remain in thedepressed position, relay lCR would be deenergized on opening switchRLS-3 in the hold circuit (line 7), opening contacts 1CR-3 of line 9. Atabout 310 of the stroke RLS-l of line 11 (the holding circuit) opensdeenergizing the clutch relays 2CR and 3CR. This prevents a restroke ofthe press until relay lCR can be reenergized by closing line 8 throughcontacts 54 and 56 of the run-jog buttons; i.e., by releasing thebuttons from the depressed position. The antirepeat relay in effectprevents a restroke should the operator hold the run-jog buttons in thedepressed position, or should they remain depressed for some otherreason.

The purpose of normally open contact CRX-1 in the hold ing circuit, line11, is to prevent the flow of current to the terminals of the dual valvecoils (through the contacts of relays 2CR and 3CR and the normally openswitch 74 of PS2) unless the clutch valves are already in an openposition; i.e., unless contacts 78 and 82 (lines 14 and 14A) of theswitches LSA and LSB are closed and relay CRX energized. This will bediscussed in greater detail.

Also responsive to the relay CRX are normally closed contacts CRX-2 andCRX-3 in lines 3 and 4 respectively.

Requiring mention at this point is switch RLS-4 in line 5 in parallelwith the normally closed contact CRX-3. Actuation of the dual clutchvalve spools causes the CRX-3 contact to open and the current to flowthrough RLS-4. Referring to H6. 2A, it can be seen that this switch isopened at about 340, at which point the flow of current to relay M isthrough CRX-3 (closed at about 300 with deenergizing relay CRX onopening the clutch valves). Switch RLS-4 is opened only momentarily:

for the purpose of checking that the important interlocking relay isoperative.

in operation, pressing the motor-start button 32 in line 3 energizesrelay M- which in turn closes hold contacts M-S in flow to the dualclutch valve coils is maintained through the holding circuit of linelll, including the closed (normally open) contacts CRX-l, of this line,and the closed (normally open) contacts 74 of switch PS-Z, of the sameline.

The master solenoid valve coil 70, line 14, remains energized by virtueof the flow of current through the closed (normally open) contactsZCR-ll, -2 and 3CR-ll, -2 of lines 10 and ll to relays ZCR, 3CR, closingthe contacts ZCR-B and 3CR-3 in line 15.

Switch RLS-3 of the hold circuit (line 7) for relay llCR opens at about200, and at this point the antirepeat relay lCR becomes deenergizedsince the normally closed contacts ZCR- 4 and 3CR-4 in line 8 are in anopen condition, and remain open until near the end of the press stroke(about 300) when RLS-l (line 11 opens deenergizing relays ZCR and 3CR.Contacts 72 of pressure switch PS2, and 76, 80 of switches LSA, LSB alsoprevent llCR from being reenergized.

At this point (about 300) the master solenoid valve coil and dual clutchvalve coils (lines 15, M and 12) also become deenergized (as the ZCR and3CR contacts open) disengaging the press clutch.

Also at this point, contact lCR-Z in line 4 closes to its normallyclosed position. Since RLS-Z (line 5) opens shortly after RLS-3 opens,at about 220, the hold current for relay M from then on is throughllCR-Z and RLS-4 in series. Ultimately, at about 340 RLS-4 opensmomentarily.

With deenergizing relays ZCR and 3CR in lines 9 and 10, the dual clutchvalve and master solenoid valve close, as well as contacts 2CR-4 and3CR-4 in line 8. Relay CRX in line 14 4 is deenergized closing contactsCRX-2, -3, lines 3 and 4 readying the press for restarting. Also topermit restarting, switch RLS-3, line 7, contacts 72, 76, 78, line 8,and switches RLS-2 and RLS-4 have been closed.

For jogging the press, the jog-run selector switch 46 is shifted so thatthe contacts 48 for this switch in line 12 are line 4 to maintain a flowof current to the relay after the motor-start button is released. Alsoclosed are contacts M-4 in line 7 for energizing the clutch circuit K.

Relay lCR also is energized closing contacts 1CR3 in line 9 so that ondepressing the run-jog buttons 50, 52 relays ZCR and 3CR are energized.This closes the contacts to the dual clutch valve and master solenoidvalve coils, energizing these coils, opening the respective valves andcausing the clutch to be engaged with the running motor, and the presscrankshaft to be turned.

it should be noted at this point, that contacts lCR-2 and CRX-3 in line4 are now in the open position actuated by energized relays llClR andCRX, line 14, the latter with opening of the dual clutch valve.Accordingly the hold current to motor relay M is through switches RLS-2(closed to about 220) and RLS-4 (closed to about 340).

While the run-jog buttons (50, 52) are depressed, the hold current forrelay lCR is through switch RLS-3 (line 7) which is closed at start ofthe press, and opened at about 200.

The operator must hold the run-jog buttons depressed for a predeterminedpart of the stroke, in this case about 160, until switch RLS-ll in lineit is closed. After this point the current closed and those of line 7(44) are open. The press is jogged in its cycle by pressing the run-jogbuttons 50, closing the contacts 62, 64, in line 12, permitting the flowof current to the relays ZCR and 3CR and to the input terminals of thedual clutch valve coils 66, 68. This closes the 2CR-3 and 3CR-3 contactsin line 15, permitting the flow of current to the input terminals of themaster solenoid valve as well. On release of the run-jog buttons, thecurrent flow is terminated, disengaging the clutch and stopping thepress slide. i The safety features of the control are as follows.

If any of the relays, the motor-starter relay M, the antirepeat relayllCR, the clutch-circuit relays ZCR, 3CR, or the interlocked relay CRXfail in the deenergized position, the press cannot be cycled. The sameis true for the solenoids for the stroke in the event the run-jogbuttons 52 remain in the depressed position. The relay is deenergized onevery stroke by switch RLS3 opening the contacts lCR-l. However, if thisrelay were to fail in the energized position, the press could repeat;i.e., without the important step of depressing the run-jog buttons,since contacts MIR-3 in line 9 would be closed. This is avoided inaccordance with the present invention by providing the normally closedcontacts tCR-ll in motor start line 3 which, would be in an open statepreventing motor relay M from being energized (with pressing of themotor-start button). lf relay llCR sticks in the open position after thepress motor has started, hold line 4 for relay M also is provided with anormally closed contact llCR-Z responsive to relay llCR, and in thiscase the press motor would stop when switch RLS-Z in parallel with lCR-Zis opened, at about 210.

Other critical relays are 2CR and BCR and it has already been mentionedthat the use of these two relays in series provides substantial safetywith respect to engagement of the clutch, in this case actuation of boththe dual clutch valve and master solenoid valve. in this case, and inconventional systems, the relays prevent actuation of the clutch valves(through the switch RLS-l should the switch stick in the U closedposition) prior to depressing the run-jog buttons. However, should bothrelays fail in the energized position, then the 2CR and 3CR contacts,lines 10. 11, and 15 would be closed and the dual clutch valve coilswould be energized. Also the master solenoid valve coil would beenergized allowing air to get to the clutch. To prevent this thenormally opened contacts CRX-l of relay CRX are provided in line I1,which would not be closed until the dual clutch valve is first closed(by virtue of contacts 82 and 78, lines 14 and 14A). Also preventingenergizing of the dual clutch valve coils, should 2CR and 3CR fail inthe energized position, are normally closed contacts 2CR-4 and 3CR4 inline 8, preventing the flow of current to relay lCR, and closing ofcontacts ICR-l in line 9. A

should the relay CRX in line 14 fail in the energized posi tion, aninterlock again is provided which includes normally closed contactsCRX-2, -3 in lines 3 and 4, which would open preventing the flow ofcurrent in these lines to the motor relay M either at start or duringhold. This interlocking is similar to that employed with respect torelay lCR, except in this case. the motor would stop on opening ofswitch RLS-4 of line 5 in parallel with the CRX-3 contact in line 4.

The interlocking relay CRX is an important relay. After substantial use,these relays can become sluggish delaying their being deenergized. As analternative, it may be desirable to connect line 14 to line 3 ahead ofthe motor-start button to prevent cycling of the press should the relaybecome sluggish. The relay would thereby remain energized and contactsCRX- 2 and CRX-3 would remain open.

Provision also is made in the circuit for: failure of the dual clutchvalve F should it be stuck in the open position, whether from residualmagnetism or sticking of any combination of internal components in thevalve body; and for failure of the master solenoid valve E in the openposition. With respect to the former, opening of the dual clutch valvecloses the contacts 78 and 82 in line 14, energizing relay (IRX, openingthe normally closed CRX-2, -3 contacts in lines 3 and 4. This preventsthe flow of current to the motor relay on pressing the motor-startbutton, or during hold. In this respect, if the dual clutch valve wereto become stuck while the press was stroking, the CRX-3 contact in line4 would remain open, and when limit switch RLS-4 (line 5) opens, themotor would be stopped. In addition, the contacts 76 and 80 in line 8would be open, preventing the clutch relays ZCR and 3CR from beingenergized. This would prevent the press from being stroked, as themaster solenoid valve could not be energized, contacts 2CR3 and 3CR-3 inline 15 being in the open position.

With respect to the master solenoid valve, should this valve fail in theopen position, the switch PS-2 contacts 72, in line 8, would openopening the run-jog circuit preventing the clutch from being engaged.

It should be apparent that the present invention affords novel andimproved circuit and interlock arrangement by which a single strokepress can be effectively prevented from starting in the event of amalfunction, or from inadvertent repeat cycles.

Although the principles of the present invention have been describedwith respect to a single stroke press, it should be apparent to thoseskilled in the art that they can be equally as well applied to a presswhich is adapted for continuous stroking, as well as single stroking andjogging.

Also, although the invention has been described with reference tospecific embodiments, variations within the scope of the followingclaims will be apparent to those skilled in the art.

lclaim:

I. A machine control comprising:

a clutch mechanism C and pneumatic circuit FIG. 1 for actuating theclutch mechanism; including a clutch valve F. and a master solenoidvalye E in series therewith;

clutch relay means ZCR, 3CR including normally open contacts 2CR-l 2,3,.and 3CR-l. 2, 3, in said clutch valve 7- l1 and master solenoid valvecircuits 15;

dual pushbutton means (50) to energize said clutch relay means ZCR 3CR;v

a holding circuit 11 in parallel with said dual pushbutton means;

an antirepeat relay circuit 8 and antirepeat relay means ICR includingnormally open contacts lCR-3 in series with said clutch relay means; and

said control further comprising interlocking switch means 72, 74, 76, insaid holding circuit 11 and antirepeat relay circuit 8 responsive to thepositions of said clutch and master solenoid valves. 7

2. A control according to claim 1 further comprising: I

interlocking relay means CRX including an interlocking relay circuit 14;

normally closed series disposed contacts CRXZ, 3 and lCR-l, 2 in serieswith said motor relay circuit CL, CL, M responsive to said interlockingrelay means CRX and said antirepeat relay means lCR;

holding switch means RLS-Z and 4 in parallel with said series disposedcontacts operative to energize said motor relay circuit CL CL, M for apredetermined part of the machine stroke; and

said interlocking relay circuit including switch means 78, 82

responsive to the position of said clutch valve F.

3. A control according to claim 2 further including normally opencontacts CRX-l in said holding circuit, in parallel with the dualpushbutton means, responsive to said interlocking relay means CRX.

4. A control system for a press having fluid actuated clutch means Cdriven by motor means B comprising: electrical motor control circuitmeans J for energizing said motor means B, a pneumatic circuit FIG. 1including electrically operated pneumatic valve means F for actuatingsaid clutch means C, an electrical run circuit FIG. 2 for operating saidvalves means F. said run circuit FIG. 2 including relay means CRX havingmotor control circuit contacts CRX-2 and CRX-3 in said motor controlcircuit 1, said run circuit including valve operated contact means 78 or82 operated by said valve means F for operating said relay means CRXsaid opening of valve means F maintaining said valve operated contactmeans 78 or 82 in a condition for preventing closing of said motorcircuit contacts CRX-Z and CRX-J by operation of said relay means CRX,whereby sticking of said valve means in an open position preventsdriving of said clutch means C by said motor means B.

5. The control system of claim 4 wherein said run circuit includesantirepeat relay means ICR, and second valve operated contact means 76or 80 connected in series with said antirepeat relay means forpreventing operation of said antirepeat relay means through said secondvalve operated contact means when said valve means is in an openposition.

6. A control system for a press having fluid actuated clutch means Cdriven by motor means B comprising; electrical motor control circuitmeans I for energizing said motor means B, a pneumatic circuit FIG. 1including master valve means E connected in series with dual valve meansF for actuating said clutch means C, an electrical run circuit FIG. 2for operating said valve means E and F, said run circuit FIG. 2including a pair of relays lCR and CRX having motor control circuitcontacts lCR-l, 1CR-2, CRX-2, CRX-3 in said motor control circuit J,said run circuit including valve operated contact means 72, 76, 80, 78,82 operated by said valve means E and F and connected in series withsaid relay means lCR and CRX, sticking of either of said relay means lCRor CRX in an energized condition maintaining at least certain of saidmotor-control circuit contacts lCR-l and lCR-2 or CRX-Z and CRX-3 in anopen position to prevent energization of said motor through said runcircuit for repeat cycles of said press, failure an electrical runcircuit FIG. 2 which actuates the clutch valve F and master solenoidvalve E; including; a motor relay circuit 15; all in parallel;

of either of said valve means E or F in an open position maintaining atleast certain of said valve operated contacts 72 or 76 or 80 in an openposition to prevent energization of at least one of said relays lCR forrepeat cycles of said press, and failure of at least one of said valvemeans F in an open position maintaining at least certain of said valveoperated contacts 78 or 82 in a closed position to maintain the other ofsaid relays CRX energized and hold at least certain of saidmotor-control circuit contacts CRX-2 and CRX-3 in an open position forpreventing energization of said motor means (B) in repeat cycles of saidpress.

7. A press control system comprising: a clutch mechanism C; a pneumaticmeans for actuating said clutch mechanism C; air supply means D; a dualclutch solenoid valve between said air supply means and said pneumaticmeans F; an electrical run circuit for said press comprising FIG. 2; amotor relay circuit L 0L, M and a dual clutch valve solenoid circuit7-11 in parallel; a first normally closed contact means in series withsaid circuits lCR-l, 1CR-2; said clutch circuit including first 9 andsecond 11 parallel lines connected to the dual clutch valve solenoids,66 and 68 the first line containing dual pushbutton contacts 58 and 60in series; the second line containing a normally open holding switchRLS-1 to energize the clutch valve solenoids 66 and 68 when thepushbuttons are released; an antirepeat relay means lCR; normally opencontacts lCR-3 responsive to the antirepeat relay means lCR in serieswith said clutch valve solenoid, 66 and 68 said first normally closedcontact lCR-l, llCR- 2 means being responsive to the antirepeat relaylCR;

the improvement comprising:

a master solenoid valve E between said air supply means D and said dualclutch solenoid valve F;

air pressure switch means PS-2 responsive to the pressure on the outputside of said master solenoid valve E;

a master solenoid valve circuit in parallel with said first and secondparallel circuits;

a second normally closed contact means CRX-Z CRX-3 in series with saidcircuits;

interlocking relay means CRX including normally open contacts CRX-l inseries with said holding switch RLS-l; the second of said normallyclosed contacts CRX-l being responsive to said interlocking relay meansCRX;

normally open switch means 78 and 82 in series with said interlockingrelay means CRX closed when said clutch valve F is energized to the openposition;

normally closed switch means '72, 76, in series with saidantirepeatrelay means 1(CR) opened when said clutch valve F or mastersolenoid valve E;

either or both, are actuated to the open position; and

normally open switch means 74 also in series with said holding switchclosed when said master solenoid valve 79 and E is actuated to the openposition.

